Considerable effort has been made to develop a plastic non-hermetic encapsulant for electronic devices which protects such devices from the environment to a degree comparable to that provided by hermetically sealed packages, but which is easier to make than hermetically sealed packages. The papers, "Electrical Performance and Reaction Kinetics of Silicone Gels," C. P. Wong, Journal of Material Research, Vol. 5, No. 4, April 1990, pp. 795-800, and "Understanding the Use of Silicone Gels for Nonhermetic Plastic Packaging," C. P. Wong et at., IEEE Transactions on Components, Hybrids and Manufacturing Technology, Vol. 12, No. 4, December 1989, pp. 421-425, describe the use of silicone resins as encapsulants for electronic devices, particularly integrated circuits. Such encapsulants typically encase the device and adhere both to the device and a substrate on which the device is mounted.
Although silicone encapsulants provide a significant measure of protection from the environment, our studies have indicated that, with ever higher requirements for the dependability of integrated circuits, even greater reliability is needed. Particularly under extreme conditions of temperature and humidity, and with high integrated circuit bias voltages, failures of the integrated circuits may still occur. With certain complex circuits, more protection is required because only a minute amount of corrosion of a conductor can cause a failure. There is therefore a continuing need for integrated circuit encapsulants that give a higher degree of protection from outside contaminants, particularly under conditions of high temperature and humidity, or with high voltage or current conduction by the encapsulated integrated circuit. Methods for applying the encapsulants should not require materials that are hazardous to the environment.